docs: def request_sign_out(self, user):
          """
          Send a single logout request to each service accessed by a
          specified user. This is called at logout when single logout
          is enabled.
  
          If requests-futures is installed, asynchronous requests will
          be sent. Otherwise, synchronous requests will be sent.
          """
          session = Session()
          for ticket in self.filter(user=user, consumed__gte=user.last_login):
              ticket.request_sign_out(session=session)